JPH0717295B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming apparatus such as a copying machine or a printer. More specifically, the present invention relates to an image forming apparatus such as a copying machine, a printer, and the like. The present invention relates to an image forming apparatus provided with a discharge roller having a function of carrying the sheet again in the direction opposite to the discharge direction.

[Prior Art] Taking the case of a copying machine as an image forming apparatus, a conventional technology will be described with reference to FIG. This is a sectional view of a copying machine capable of performing not only single-sided copying but also double-sided copying and multiplex copying.

The copying machine 1 has a copying machine main body 3 having an image forming section 2 built therein. The copying machine main body 3 is provided with an original placing table 5, a light source 6 and a lens 7, and a cylindrical shape is formed by these optical systems. A latent image corresponding to the original is formed on the photoconductor 10 of FIG. Around the photosensitive member 10, a primary charger 13, developing devices 11a and 11b containing toners of different colors, a transfer charger 15, a separation charger 16,
And the cleaner 12 is arranged in order.

In addition, the paper feed roller 1 is provided near the leading end of the paper feed cassettes 9a and 9b.
9a and 19b are provided, and the transfer sheet S is guided to the registration roller pair 22 via the pair of conveying rollers 20a and 20b and the sheet feeding and conveying paths 21a and 21b, respectively.

Then, the transfer sheet S sent out from the pair of registration rollers in synchronization with the movement of the photoconductor 10 has a toner image transferred by the transfer charger 15 and separated from the photoconductor 10 by the separation charger 16 to reach the conveying device 17. . Further, a fixing device 25 is disposed behind the conveying device 17, and a first discharging roller pair 26 is provided on the rear side of the fixing device 25 and a transfer sheet is usually provided as a second discharging roller pair 27. It is arranged to be discharged to a tray or the like outside the machine via the. A flapper 29 and an auxiliary flapper 30 are arranged between the first discharge roller pair 26 and the second discharge roller pair 27, and the transfer sheet normally discharged from the first discharge roller pair 26 is provided. S is conveyed along the upper side of the flapper 29 at the solid line position, and its conveying force causes the auxiliary flapper 30 which is swingably supported by the support shaft 30a to swing in the arrow direction about the support shaft 30a. Further, the leading end of the transfer sheet S has a detection arm 3 which is swingably supported by a support shaft 31b.
By pushing up the detection unit 31a of 1 and swinging the detection arm 31 clockwise around the support shaft 31b, the optical sensor 32 is operated and the passage of the transfer sheet is detected. Then, the transfer sheet S is discharged to the outside of the machine by the second pair of discharge rollers 27 which rotate in the normal direction.

During double-sided copying, the transfer sheet S is partially discharged to the outside of the machine by the forward rotation of the second discharge roller pair 27 as in the normal state, but the rear end of the transfer sheet is used as an auxiliary member. The second discharge roller pair 27 is reversely operated by the operation of the detection arm 31 and the optical sensor 32 at the time of leaving the flapper 30, and the transfer sheet S is thereby guided to the left side portions of the auxiliary flapper 30 and the flapper 29 so that both sides thereof are guided. It is adapted to be introduced into the transport path 33. Therefore, when copying on both sides,
The second discharge roller pair 27, the flapper 29, the auxiliary flapper 3
By being sent to the double-sided transport path 33 via 0, the detection arm 31, the optical sensor 32, etc., the transfer sheet S is switched back, the front and back sides are reversed, and transported again to the registration roller pair 22.

Further, in the case of multiple copying, the flapper 29 is switched to the state in which the right end portion is turned up, and the transfer sheet discharged from the first discharge roller pair 26 is also guided by the right side portion of the flapper 29 so that the double-sided conveying path is also formed. It will be introduced to 33. Therefore, at the time of multiple copying, the first discharge roller pair 2
By being sent to the double-sided conveying path 33 via the flapper 29, the transfer sheet S is sent to the registration roller pair 22 without being turned upside down. Then, the transfer sheet S introduced into the double-sided conveyance path 33 is passed through a pair of conveyance rollers 35, 36 and a sheet conveyance section 23 having a lateral registration means 37 for aligning one lateral end of the transfer sheet S to a reference position. The pair of registration rollers 22 are guided.

As described above, in the copying machine 1, when the multiple copy or the double-sided copy is performed on the same transfer sheet, the transferred transfer sheet S carried out through the image forming unit 2 and the fixing device 25 is
The sheet is re-introduced into the image forming section 2 through the sheet re-feeding means such as the flapper 29 and the sheet conveying section 23. At that time, the horizontal positioning and the vertical positioning of the transfer sheet S are performed. The lateral registration means 37 and the pair of registration rollers 22 are arranged to align one lateral end and the leading edge of the transfer sheet S in a prescribed position.

By the way, the second discharge roller pair 27 configured to be capable of forward and reverse rotations.
Must have the original function of firstly stacking the transfer sheets S on the discharge tray 38 in an orderly manner.
For this reason, it is desirable that the transfer sheet S to be discharged be attached to the waist, and the leading end of the transfer sheet S is sent as far as possible without coming into contact with the discharge tray 38. FIG. 4 shows a structure for stiffening the transfer sheet S. Both ends of the discharge roller 39, which is the lower roller of the second discharge roller pair 27, have a larger diameter than that. Flange 41 is provided, and the discharge roller
The driven roller 40 is in contact with 39 from above. As a result, the transfer sheet S is bent as shown in the figure, and the waist is attached. As shown in FIG. 5, the transfer sheet S ejected when the flanges 41 are not provided at both ends of the paper ejection roller 39 has its leading end dropped on the front side of the paper ejection tray 38 as shown by the solid line. The leading edge of the transfer sheet S, which has been stiffened by the flange 41, reaches farther as shown by the broken line. Therefore, the contact resistance with the discharge tray 38 or another transfer sheet already discharged and stacked on the discharge tray 38 is reduced, and the stacking at the time of discharging is smoothly performed.

[Problems to be Solved by the Invention] In order to stack the transfer sheets S on the discharge tray 38 in an orderly manner, it is necessary to push the rear end of the transfer sheets S toward the outside of the machine. Explained eject roller 39 and flange 41
With the construction of only chisel, the pop-out force is insufficient. FIG. 6 (a) shows the state of discharge when this configuration is used.
The vicinity of the rear end portion of the transfer sheet S is abutted with the discharge roller 39. This is because the contact resistance between the transfer sheet S and the discharge tray 38 cannot be overcome only by the frictional force between the discharge roller 39 and the transfer sheet S. As a measure against this, conventionally, the sixth
A protrusion protruding around the flange 41 as shown in FIG.
It has been practiced to dispose 41a in a radial pattern and push the trailing end of the discharged transfer sheet S by hooking it as shown in the figure. According to this method, regardless of the material of the discharge roller 39,
There is an advantage that the transfer sheet S can be reliably ejected.

However, on the other hand, according to this method, when the surface of the transfer sheet S and the corner of the protrusion 41a come into contact with each other, the transfer sheet S
There is an inconvenience that the mark of the corner is attached to.
When it is necessary to reverse the paper discharge roller 39 in the forward and reverse directions for double-sided copying, the reverse rotation of the paper discharge roller 39 causes another
Traces of corners of the protruding protrusions 41a are attached to the transfer sheet S. Therefore, in the worst case, when the second side is copied, a transfer failure (a toner image is not transferred) occurs in the portion where the mark is present. Furthermore, this protrusion
Due to the presence of 41a, the transfer sheet S is fed while vibrating up and down, so that when the leading edge (the trailing edge until now) of the transfer sheet S that is re-conveyed in the opposite direction for double-sided copying contacts the flapper 30. Depending on the behavior of the top and bottom, it may turn up, which may cause a jam.

[Structure for Solving the Problem] The structure of the present invention for solving the above-mentioned problems of the prior art includes an image carrier that carries a toner image and transfers the toner image onto a sheet material, and Discharge that contacts the surface on which the toner image is not transferred by the image carrier and rotates normally to discharge the sheet material, or that rotates in the normal direction to switch back after being conveyed in the discharge direction. A roller, a pressing unit that cooperates with the discharge roller to hold the sheet material, and a sheet material switched back by the discharge roller to transfer the toner image to the surface on which the toner image is not transferred. The transport means transports the image to the image carrier, and a protrusion that is disposed at an end portion of the discharge roller and applies a protrusion force to the sheet material to be discharged. The protrusion is one side surface of the protrusion. And a protrusion side end face which is provided at a steep angle with respect to the peripheral surface of the discharge roller and abuts on the rear end portion of the sheet material to be discharged to give a protrusion force, and which is one side surface of the protrusion An image forming apparatus, comprising: a reverse-feed side end surface that is located on the opposite side of the delivery-side end surface and that is provided at a gentle angle with respect to the discharge roller peripheral surface.

[Embodiment] FIG. 1 shows a first embodiment of the present invention. Eight projections 41b are provided on the peripheral surface of the flange 41. When the discharge roller 39 rotates in the forward direction (counterclockwise) to discharge the transfer sheet S, the projections 41b are provided. The protruding side end portion 41b 'hooks the rear end portion of the transfer sheet S to give a protruding force. Further, as shown in FIG. 2, when the discharge roller 39 rotates in the reverse direction (clockwise), the reverse feeding side end portion 41b ″ of the protrusion 41b forms a gentle inclined portion, and At that time, no traces are left on the transfer sheet S, and the transfer sheet S is not conveyed with vertical movement due to a sudden step.
The above-mentioned inconvenience does not occur.

FIG. 3 shows a second embodiment of the present invention. In the first embodiment, the angle of the protrusion side end portion 41b 'of the protrusion protrusion 41b is approximately 90 degrees, but in the present embodiment, the angle of the protrusion side end portion 41c' is 90 degrees. Also large θ
Is set to. According to this configuration, when ejecting the transfer sheet S, a certain amount of pop-out force is applied,
In addition, it is possible to make it difficult for the transfer sheet S to be marked even when the discharge roller rotates in the normal direction.

As shown in FIG. 3, in order to give a difference in the protrusion force between the forward rotation and the reverse rotation, it is sufficient to set θa and θb to different magnitudes. θa is a protrusion side end portion 41c ′ and the discharge roller 39
Is an angle formed by a normal line standing upright with respect to the peripheral surface of, and θb is an angle formed by the reverse feeding side end portion 41c ″ and the normal line.
The smaller a and θb are, that is, the steeper the inclination is, the greater the protrusion force to the rear end of the transfer sheet S is. Further, the larger the θa and θb are, that is, the smaller the inclination is, the smaller the protrusion force is and the less the trace is left on the transfer sheet S. Similarly, the larger θa and θb are, the smaller the vertical movement of the transfer sheet S due to the sudden step can be suppressed. Therefore, if the ejection force is not required as in the case where the discharge roller 39 rotates in the reverse direction and the transfer sheet S is conveyed in the reverse direction, θb
Is preferably made as large as possible so as not to affect the transfer sheet S and its conveyance.

[Advantages of the Invention] As described above, according to the present invention, the discharge roller is provided with the reverse-feeding-side end surface of the protrusion for protruding when the sheet material is discharged, with respect to the peripheral surface of the flange. When the sheet is rotated in the reverse direction, the protrusion does not leave a mark on the sheet material to reduce transfer defects, and the vertical movement when the sheet material is conveyed in the reverse direction can be reduced, so that a stable conveying state can be maintained.

[Brief description of drawings]

FIG. 1 is a side view of an essential part showing a state in which a paper discharging roller is rotating in a forward direction in a first embodiment of a sheet material discharging device using the present invention, and FIG. 2 is a paper discharging roller of FIG. Is rotating in the opposite direction, FIG. 3 is a side view of the essential parts showing a second embodiment of the sheet material discharging device using the present invention, and FIG. 4 is a discharge roller. FIG. 5 is a front view showing the relationship of the flanges, and FIG. 5 is a comparative view showing the discharge state of the sheet material with and without the flange for mounting the sheet material on the waist,
FIG. 6 (a) is a side view of a main part of a conventional sheet material discharging device having a protrusion for protrusion, and FIG. 6 (b) is a main part of a sheet material discharging device having no protrusion for protrusion. A side view, FIG. 7 is a side view of essential parts showing a state in which a paper discharge roller is rotating in a reverse direction in a conventional sheet material discharging device having a protrusion for protrusion, and FIG. 8 is a sheet material according to the present invention. It is sectional drawing of the copying machine which can apply an ejection device. 29 …… Flapper, 30 …… Auxiliary flapper, 38 …… Discharge tray, 39 …… Discharge roller, 40 …… Following roller, 41 …… Flange, 41a, 41b, 41c …… Extrusion protrusion, 41b ′, 41c ′ …… Extrusion side end surface, 41b ″, 41c ″ …… Reverse feeding side end surface.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Ozawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Toshihiko Kusumoto 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (72) Inventor Naoki Okuda 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Michio Koike 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. ( 72) Inventor Atsushi Kubota 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Akiyoshi Kimura 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Nobukazu Sasaki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Masashi Ohashi 3-30-3 Shimomaruko, Ota-ku, Tokyo No. Canon Inc. (72) Inventor Yasuyoshi Yamamoto 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) Reference Japanese Patent Laid-Open No. 57-162091 (JP, A) No. 58- 154950 (JP, U)

Claims (2)

[Claims] 1. An image bearing member carrying a toner image and transferring the toner image onto a sheet member, and a sheet member contacting a surface of the sheet member on which the toner image is not transferred, A discharge roller that rotates normally to discharge the material, or that rotates in the discharge direction and then rotates in the reverse direction to switch back after switching back, and a pressing unit that clamps the sheet material in cooperation with the discharge roller, Conveying means for conveying the sheet material switched back by the discharge roller to the image carrier for transferring the toner image to the surface on which the toner image has not been transferred, and disposed at the end of the discharge roller. And a protrusion that gives a protruding force to the sheet material to be discharged, the protrusion being one side surface of the protrusion and provided at a steep angle with respect to the peripheral surface of the discharge roller, and the sheet material to be discharged. The protrusion side end surface that abuts the rear end portion to give a protrusion force, and one side surface of the protrusion, which is located on the opposite side of the protrusion side end surface and at a loose angle with respect to the discharge roller peripheral surface. An image forming apparatus comprising: a reverse feeding side end face provided. 2. The image forming apparatus according to claim 1, wherein the pressing means has a roller.